Variable Capacity Centrifugal Pump Assembly

ABSTRACT

A variable capacity centrifugal pump assembly including a bearing housing, an impeller shaft rotatably mounted within the bearing housing and projecting therefrom, a volute circumscribing a cavity therein, a plurality of differently sized impellers for mounting on the impeller shaft within the cavity, a wear plate secured to the bearing housing and a volute and defining a downstream end portion of the cavity, a plurality of differently configured annular front covers for mounting to an upstream end of the volute for varying the size and configuration of the cavity to accommodate one of a selected plurality of differently sized impellers. The suction intake is mounted to the upstream end of the selected cover for communicating the pipe assembly with inlet hoses of varying size whereby the capacity of the pump assembly can be varied by the selective matching of the front covers with the impellers.

BACKGROUND OF THE INVENTION

The present invention is directed to centrifugal pumps of the type commonly used in a wide variety of dewatering applications such as water removal from lakes and ponds, storm water runoff, nuisance water removal and the pumping of sewage. Centrifugal pumps utilize an impeller fixed on a rotary shaft and enclosed in a spiral-shaped casing called a volute. Rotation of the shaft causes the impeller to draw water into the volute and expel the water therefrom utilizing the centrifugal force imparted to the water by the rotating impeller. Centrifugal pumps must have a “wet” inlet in that there must be water in both the intake (inlet) pipe and the casing when the pump is started. Accordingly, such pumps must be “primed” by adding water to the intake pipe and casing prior to use. Centrifugal pumps are sized for different performance characteristics with 4, 6 and 8 inch pump sizes being the most common. The reference to inches in the sizing of the pump refers to the diameter of the water inlet hoses for which the pump is designed to be used. Other components of the pump, namely the volute and impeller as well as the motor for driving the impeller shaft also vary in size depending on the hose diameter, i.e., the size of the pump. The suction intake on centrifugal pumps which communicate the hose with the inlet side of the pump and with the priming chamber also are matched to the hose size and thus to the pump size. Also, the impeller size is matched to the size of the volute. As a result, to vary the performance characteristics of the pump for use in different applications, the entire pump assembly must be replaced. For example, if a particular application calls for an 8 inch pump (a pump designed for use with an 8 inch diameter hose), a 6 inch pump (designed for use with a 6 inch hose) cannot be readily modified to accommodate the larger 8 inch hose without a substantial degradation of performance. A different pump size is required for use with the 8 inch hose. This lack of versatility in such pumps creates inventory problems for both users and equipment suppliers.

It would be highly desirable, particularly from a cost standpoint, if the performance characteristics of these pumps could be adjusted in the warehouse or in the field for different applications or needs. Frequent renters of such equipment could significantly reduce their inventory investment and pump users similarly would benefit from the versatility as well. The present invention provides the flexibility heretofore lacking in centrifugal pumps whereby multiple hose sizes can be readily accommodated on a single centrifugal pump without degrading performance. In other words, the size or flow capacity of the pump can be readily modified by exchanging a few components. It is no longer necessary to replace the entire pump.

SUMMARY OF THE INVENTION

The present invention provides a centrifugal pump having a suction intake component configured to cooperate with differently-sized front covers and hose adapters so as to communicate efficiently one of a selected plurality of common hose sizes with the inlet side of the pump using a single suction intake component. The suction intake component of the present invention also accommodates a variety of different priming sections and in the preferred embodiment of the present invention, one of a selected plurality of differently-sized impellers are accommodated in a single volute. The interchangeability of the hose sizes with a single suction intake component and of differently-sized impellers within a single volute enable the user or the supplier to readily adjust the performance parameters of the pumps, both in the field or in the warehouse, without degrading the performance of the pump whereby the versatility of the pump is substantially enhanced so as to obviate the need to manufacture and maintain inventory of multiple pump sizes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a frontal view of a centrifugal pump assembly of the present invention.

FIG. 1B is a perspective view of a centrifugal pump assembly of the present invention.

FIG. 2 is a sectional view taken along the line 2-2 in FIG. 1B.

FIG. 2A is a sectional view taken along the line 2A-2A in FIG. 1A.

FIG. 3 is an exploded view of the pump assembly of the present invention.

FIG. 4 is an upstream perspective view of the suction intake component of the present invention.

FIG. 5 is a downstream perspective view of the suction intake component of the present invention.

FIG. 5A is a sectional view taken along the line 5A-5A in FIG. 7.

FIG. 5B is a sectional view taken along the line 5B-5B in FIG. 7.

FIG. 6 is an end view of the upstream side of the suction intake component.

FIG. 7 is an end view of the downstream side of the suction intake component.

FIG. 8A is an upstream or front perspective view of the front cover of the present invention configured for an 8 inch pump showing the direction of water flow therethrough.

FIG. 8B is a downstream or rear perspective view of the front cover shown in FIG. 8A. showing the direction of water flow therethrough.

FIG. 8C is a front end view of the front cover shown in FIG. 8A.

FIG. 8D is a rear end view of the front cover shown in FIG. 8A.

FIG. 8E is a sectional view taken along the lines 8E-8E in FIG. 8C.

FIG. 8F is a side view of the front cover shown in FIG. 8A.

FIG. 9A is an upstream or front perspective view of the front cover of the present invention configured for an 6 inch pump showing the direction of water flow therethrough.

FIG. 9B is a downstream or rear perspective view of the front cover shown in FIG. 9A showing the direction of water flow therethrough.

FIG. 9C is a front end view of the front cover shown in FIG. 9A.

FIG. 9D is a rear end view of the front cover shown in FIG. 9A.

FIG. 9E is a sectional view taken along the lines 9E-9E in FIG. 9C.

FIG. 9F is a side view of the front cover shown in FIG. 9A.

FIG. 10A is an upstream or front perspective view of the front cover of the present invention configured for an 4 inch pump showing the direction of water flow therethrough.

FIG. 10B is a downstream or rear perspective view of the front cover shown in FIG. 10A showing the direction of water flow therethrough.

FIG. 10C is a front end view of the front cover shown in FIG. 10A.

FIG. 10D is a rear end view of the front cover shown in FIG. 10A.

FIG. 10E is a sectional view taken along the lines 10E-10E in FIG. 10C.

FIG. 10F is a side view of the front cover shown in FIG. 10A.

FIG. 11A is a side view of a hose attachment used with the suction intake component of the present invention.

FIG. 11B is a rear view of the hose attachment shown in FIG. 11A.

FIG. 12A is an upstream or front perspective view of the impeller preferably used in the present invention configured for an 8 inch pump.

FIG. 12B is a downstream or rear perspective view of the impeller shown in FIG. 12A.

FIG. 12C is a rear end view of the impeller shown in FIG. 12A.

FIG. 12D is a side view of the impeller shown in FIG. 12A.

FIG. 12E is a sectional view taken along the line 12E-12E of FIG. 12C.

FIG. 12F is a sectional view taken along the line 12F-12F of FIG. 12C.

FIG. 13A is an upstream or front perspective view of the impeller preferably used in the present invention configured for a 6 inch pump.

FIG. 13B is a downstream or rear perspective view of the impeller shown in FIG. 13A.

FIG. 13C is a rear end view of the impeller shown in FIG. 13A.

FIG. 13D is a side view of the impeller shown in FIG. 13A.

FIG. 13E is a sectional view taken along the line 13E-13E of FIG. 13C.

FIG. 13F is a sectional view taken along the line 13F-13F of FIG. 13C.

FIG. 14A is an upstream or front perspective view of the impeller preferably used in the present invention configured for a 4 inch pump.

FIG. 14B is a downstream or rear perspective view of the impeller shown in FIG. 14A.

FIG. 14C is a rear end view of the impeller shown in FIG. 14A.

FIG. 14D is a side view of the impeller shown in FIG. 14A.

FIG. 14E is a sectional view taken along the line 14E-14E of FIG. 14C.

FIG. 14F is a sectional view taken along the line 14F-14F of FIG. 14C.

FIG. 15 is an enlarged partial sectional view of a centrifugal pump employing the suction intake assembly of the present invention and illustrating the relative positioning and securement of a preferred configuration of the assembly.

FIG. 16 is a partial section view taken along the line 16-16 in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now in detail to the drawings, FIGS. 1-3 illustrate a preferred embodiment of a centrifugal pump assembly 10 comprising the present invention. The pump assembly 10 is similar to and operates in the same general manner as a conventional centrifugal pump. Significant differences between pump assembly 10 and centrifugal pumps found in the prior art include the configuration of the suction intake 12 and the differently-sized and configured front covers 14 a, 14 b and 14 c that are removeably attached to the suction intake, the differently-sized hose attachments 16 a (only 16 a being shown in the drawings), the configuration of the volute 18 and the differently-sized and configured impellers 20 a, 20 b and 20 c that are accommodated with the single volute and cooperate with a correspondingly sized front cover 14 a, 14 b or 14 c, the suction intake 12 and the correspondingly-sized hose attachment to effectively provide a variable capacity pump or multiple pump sizes in a single pump assembly.

The present invention illustrated in FIGS. 1-3 provides an 8 inch size centrifugal pump for use with an 8 inch diameter hose. As seen therein, the pump comprises the suction intake 12 which is mounted to the water inlet side 19 of the pump and an appropriately-sized and configured front cover 14 a for an 8 inch pump. The front cover 14 a is disposed between and in sealing engagement with the downstream end of the suction intake 12 and the upstream end of the pump volute 18. A hose attachment 16 a, also appropriately-sized for an 8 inch pump, is in sealing engagement with and projects axially from the upstream end 12 a of the suction intake 12. An impeller key 22 locks the appropriately-sized and configured impeller 20 a for an 8 inch pump to the impeller shaft 23, also referred to as a drive shaft, with the impeller being disposed in an interior cavity 21 within the volute 18 and projecting into the front cover 14 a as seen in FIG. 2. A wear plate 24 and o-ring seals 26 a and 26 b are disposed within the volute 18 between the interior backside thereof and the backside of the impeller as illustrated in FIGS. 2 and 3.

An oil reservoir 30 is provided for lubricating the impeller shaft seals 87 a and 87 b. The reservoir 30 is carried by a mounting bracket 28 a that is secured to a pair of mounting surfaces 28 b provided atop the cover 29 a of a check valve assembly 29 provided in the volute 18 proximate the discharge end 18″ thereof. Lubricating oil from the reservoir 30 is directed through an opening 18′ in the volute 18 via conduit 33 and into an interior chamber 25 extending about the impeller shaft 23 where it lubricates seals 87 a and 87 b (see FIGS. 1B, 2 and 3).

The aforementioned check valve assembly 29 comprises a flapper disc 29 b, preferably formed of a flexible rubber material and mounted within a cavity 29 a′ in the underside of valve cover 29 a between the cover and the volute, upstream of and adjacent to the discharge end 18′″ thereof as shown in FIG. 2A. The check valve assembly 29 both allows the pump to prime when the volute 18, suction intake 12 and the suction hose (not shown) are devoid of liquid and it also prevents back flow through the pump from any external discharge system (not shown).

In a preferred embodiment of the check valve assembly 29, the flexible flapper disc 29 b defines an enlarged rear base portion 29 b′ and an extended generally planar body portion 29 b″. The base and body portions of the flapper disc also define angularly offset and generally flat lower surfaces as seen in FIGS. 2A and 3. In the particular model of the flapper disc 29 b identified below, that angle is 135 degrees. The base portion 29 b′ of the disc is disposed within the cavity 29 a′ in the underside of the valve cover as above described and the valve cover and flapper disc are secured in place by means of studs 30 a and hex nuts 30 b (see FIGS. 2A and 3). A gasket 34 is provided between the valve cover and a flat annular mounting surface 35 atop the volute (see FIG. 3). The configuration provides a fluid-tight seal between the valve cover 29 a and the volute 18, effectively clamps the enlarged base portion of the flapper disc between the valve cover and the volute and positions the flapper disc in an inclined disposition within the volute. So positioned and secured, the flat lower surface of the enlarged base of the disc bears against the volute and the underside of the extended body portion 29 b″ of the flapper disc bears against and is in sealing engagement with a similarly inclined valve seat 29 c, preferably formed of stainless steel. The seat 29 c is in turn disposed in sealing engagement with the interior surface of the volute by means of an o-ring 29 d that is preferably carried in an annular channel (not shown) in the underside of the seat and is secured in place via screws 29 e. The above described check valve assembly renders the valve seat readily replaceable, significantly prolonging the useful life of the volute. When liquid is drawn through the volute 18 by the impeller 12 a, the body portion 29 b″ of the flapper disc is flexed upwardly allowing fluid flow thereby to and through the pump discharge outlet 90. Absent such flow, the natural flex in the disc will maintain the flapper disc 29 b in its closed position against the check valve seat 29 c (see FIG. 2A). By way of example only, a flapper disc marketed by Val-Matic Valve & Manufacturing Corporation of Elmhurst, Ill., model no. 506-HP3, can be employed in pump assembly 10 as above described.

The suction intake 12 of the present invention is illustrated in FIGS. 4-7 and, as noted above, is configured to cooperate with the suitably-sized hose attachment 16 a at its upstream end 12 a and suitably-sized front cover 14 a at its downstream end 12 b, so as to communicate an 8 inch hose (not shown) with the water inlet side 19 of the pump. The hose attachment 16 a is illustrated in FIGS. 11A and 11B. The front cover 14 a is illustrated in detail in FIGS. 8A-8E. As will be further explained later herein, to convert pump 10 from an 8 inch pump to a 6 inch size pump, the front cover 14 a would be replaced with the appropriately-sized and configured front cover 14 b (see FIGS. 9A-9F) and hose attachment 16 a would be replaced with a slightly smaller but similarly configured hose attachment (not shown). Both replacement parts would be attached to the downstream and upstream ends respectively of the same suction intake 12 in the same manner as the front cover 14 a and hose attachment 16 a. For a 4 inch pump, front cover 14 c (see FIGS. 10A-10F) and a still smaller hose attachment would be used with the same volute 18 and suction intake 12. As seen in the above-identified FIGS. 8-10, while the sizes of the interiors of the front covers decrease from 14 a to 14 e, the size of the mounting flanges 58, the aperture pattern and the spacing of the mounting apertures 60 therein remain constant.

The suction intake 12 is “a one size fits all” and comprises a cylindrical body portion 38, an upstream annular mounting flange 40 projecting radially from the upstream end of the body portion and a downstream annular mounting flange 42 projecting radially from the downstream end of the body portion, and defines a fluid flow passageway 44 extending axially therethrough and an upstanding priming section mount 46 extending about an opening 48 communicating the priming system (not shown) secured to and carried by mount 46 with the central passageway 44 of the suction intake. The priming section mount is configured so as to be compatible with a variety of available priming sections, including vacuum pumps with electronic sensing level control probes and air compressor—Venturi combinations with mechanical float level controls.

The upstream mounting flange 40 on the suction intake 12 is configured to be releaseably and sealably engaged with differently-sized conventional hose adapters 16 a, such as the “Bauer” type hose connection illustrated in FIGS. 11A and 11B. As seen therein, the hose adapter 16 a is provided with a downstream annular end flange 50 that abuts the upstream end flange 40 on the suction intake about a flat faced gasket (not shown) between the flange 50 and the face of end flange 40. To effect the desired engagement of the flange 40 on the suction intake with flange 50 on the hose attachment, a plurality of threaded studs (not shown) can be received in and threadably engage a corresponding plurality (preferably eight) of equiangularly-spaced threaded blind channels 53 tapped into the upstream flange 40 on the suction intake such that the studs project axially therefrom and through aligned apertures 54 in the hose attachment flange 50, whereon the threaded end portions of the studs can be engaged by suitable threaded fastening members. Upon tightening of the fastening members about the studs, the adjacent flanges 40 and 50 are drawn together about a gasket (not shown), forming a liquid-tight seal between the suction intake 12 and the hose adapter 16 a. The upstream end portion of the hose adapter 16 a is configured to releaseably engage a corresponding fitting (not shown) on the downstream end of a conventional 8 inch pump hose. The downstream mounting flange 42 on the suction intake 12 also is provided with a plurality of spaced apertures 56 therein, again preferably eight in number, to secure the suction intake to the front cover 14 a and to the volute, as will be described.

The front cover 14 a for the 8 inch configuration of pump 10 is illustrated in detail in FIGS. 8A-8F and functions to smoothly transition the water being drawn from the 8 inch diameter hose through the suction intake into the volute while concurrently providing a forward wear surface for the correspondingly-sized impeller 20 a. The cover 14 a preferably includes a flange 58 projecting radially from a cylindrical body portion 15 proximate the upstream end of the cover, a plurality of equiangularly-spaced apertures 60, again preferably eight in number, extending axially therethrough and adapted to receive a corresponding plurality of studs 51 for the securement of the cover to the suction intake 12 and volute 18 as will be described. The body portion of cover 14 a defines an outwardly inclined surface 68 that merges at 70 into a curvilinear inner wall surface 72. The inwardly tapered surface 68 at the inlet end of the front cover 14 a is tapered as shown in FIG. 8E so as to allow liquids laden with materials to enter the pump at a low entrance angle. As liquid flows through the two channels of the impellor, the direction of flow (indicated with an arrow in FIGS. 8A, 8B and 8E) is gradually changed to where it departs the impeller at an angle of 90° with respect to the pump drive shaft 23.

The outwardly inclined and curvilinear inner wall surfaces 68 and 72 on front cover 14 a collectively define the forward wear surface for the impeller 20 a as wall surfaces 68 and 72 are shaped and sized so as to maintain a constant tolerance of about 0.020 in. between the wall surfaces 68 and 72 and the trailing end surfaces 73 a and 74 a of the impeller blades 73 and 74. A plurality (three being shown) of washout grooves 75 are disposed in the tapered and curvilinear wall surfaces 68 and 72 for the purpose of diverting entrained material such as grit from the wall surfaces and the corresponding surfaces on the two impeller blades 73 and 74. Additionally, these grooves 75 provide a cutting action on long fibrous materials to prevent pump clogging. Cover 14 a also defines annular recessed areas 76 and 78 (see FIGS. 3 and 8 a and 8B) to accommodate o-rings seals 80 and 82 and provide a liquid-tight sealing engagement of the cover with annular wall surface 12′ of the suction intake and with the volute 18 respectively.

The above-described front cover 14 a is secured to the suction intake 12 and the volute 18 in a liquid-tight disposition by a plurality of threaded studs 51 and o-rings 80 and 82. Studs 51 threadably engage a corresponding plurality of blind tapped channels 51′ in the volute 18 (see FIG. 15) and extend about the impeller 20 a and back wear plate 24 and through one or more axially aligned spacing members, preferably in the form of annular shims, (three being shown in FIGS. 3-27 a, 27 b and 27 c) and through the aligned apertures 56 in the downstream end of radial flange 42 on the suction intake. The ends of studs 51 protruding from the upstream end of flange 50 are threadably engaged by suitable fastening members 55.

As is also seen in FIG. 15, a plurality of suitably long threaded studs 62 threadably engage a corresponding plurality of blind tapped channels 62′ in the downstream end of the back wear plate 24 and extend downstream therefrom through apertures 63 in the downstream end of the volute 18, through aligned apertures 65 in the mounting flange 86 at the forward end of the bearing housing 31 whereupon the protruding downstream ends of studs 62 are threadably engaged by fastening members 67. In a preferred embodiment of the invention, four such studs 62 are employed. In addition, a second plurality of suitably long threaded studs 62 a threadably engage a corresponding number of threaded channels (not shown) within the volute 18 and extend downstream through the mounting flange 86 on the bearing housing where the studs 62 are threadably engaged by fastening members 67 a whereby the above-described pump components are secured and held together in a tight disposition with the impeller 20 a being mounted on the impeller shaft 23 and locked in place within the interior cavity 21 in the volute 18 by the aforesaid impeller key 22 and a socket head cap screw 23′. Cavity 21 is defined by opposed portions of the volute, the back wear plate 24 and wall surfaces 68 and 72 on the front cover. Through such a configuration, a clearance of about 0.020 in. is maintained between the back wear plate 24 and the trailing surfaces 73 a and 74 a of the impeller blades 73 and 74 and between the wall surfaces 68 and 72 of the front cover and the leading edges of the impeller.

The above-referenced annular shims 27 a-c can be positioned between the volute and front cover to adjust the clearance between the curved front surface of the impeller and the front cover. By adding or deleting one or more shims, the distance between those surfaces can be adjusted to obtain the desired clearance of about 0.020 inches. The shims 27 a-27 c are preferably formed of a plastic material, define apertures 27′ therein for the passage of studs 51 therethrough and preferably vary in thickness. By way of example, shim thicknesses of 0.005 in., 0.010 in. and 0.020 in. may be employed for shims 27 a-27 c. Also, additional shims and different thicknesses could be utilized to provide the desired clearance.

The bearing housing 31 contains bearings 32 for supporting the rotatably-mounted impeller shaft 23 therein as seen in FIG. 2. The bearing housing also defines the previously identified mounting flange 86 at the forward end thereof and an enlarged chamber 88 disposed about the rearward end of the impeller shaft so as to accommodate the connection of the impeller shaft 23 to an engine (not shown) via mounting flange 89. The discharge outlet 90 on the pump 10 communicates with the volute in a conventional manner and is provided with an annular mounting flange 91 preferably having a plurality of blind threaded channels 94 therein for receiving a corresponding plurality of studs and an annular recess for receiving a flat face gasket seal (not shown) for a tight securement to a conventional hose attachment using threaded fasteners so as to releaseably connect the discharge outlet 90 on the pump 10 with an appropriately-sized conventional pump hose (e.g., an eight, six or four inch hose).

As indicated earlier herein, to modify pump 10 to a 6 or 4 inch pump size, the front cover 14 a and hose attachment 16 a are simply removed from the downstream and upstream ends of the suction intake and replaced with either the 6 or 4 inch size hose attachment and front cover 14 b (for a 6 inch pump) or 14 c (for a 4 inch pump). In addition, the impeller 20 a is replaced with either impeller 20 b, sized and configured for a 6 inch pump, or impeller 20 c, sized and configured for a 4 inch pump. The different hose attachments vary in size to match 8, 6 and 4 inch diameter hoses, but all three attachments have the identical aperture patterns on their end frames 50. Accordingly, the differently-sized hose attachments are interchangeable and easily replaced on upstream mounting flange 40 on the suction intake volute studs and fastening members 55. Also because of their similarity, only attachment 16 a is illustrated in the drawings (see FIGS. 11A and 11B). Similarly and as previously noted, front covers 14 a, 14 b and 14 c also have identical aperture patterns in their radial flanges 58 whereby the differently-sized front covers are interchangeable with respect to the suction intake 12 and the volute 18 via threaded studs 51. By way of example only, representative dimensions of preferred front cover configurations for 8, 6 and 4 inch pump sizes are set forth in FIGS. 8E and 8F, 9E and 9F and 10E and 10F. Similarly, representative dimensions of preferred impeller configurations for 8, 6 and 4 inch pump sizes are set forth in FIGS. 12E and 12F, 13E and 13F and 14E and 14F. Other dimensions and configurations could be employed in the present invention to provide these and other pump sizes.

Impellers 20 a, 20 b and 20 c also are readily interchangeable on the impeller shaft 23 via impeller key 22 and socket head cap screw 23′ in that the size of the cavity 21 formed within volute 18 in which the impellers are disposed, varies in accordance with the configuration of the interior walls of the front covers 14 a, 14 b and 14 c. While the length or axial dimension of the impellers increase with the pump size, the length or the axial dimension of the front covers decrease with pump size whereby the earlier referenced 0.020 in. tolerance between the impeller and the back and front wear plates is maintained. In each case, the base of the impeller remains the same distance from the back wear plate 24. The variation in sizes and dimensions between impellers 20 a, 20 b and 20 c and their respective front covers 14 a, 14 b and 14 c is set forth in detail in FIGS. 12-14 and 8-10. As a result of this coordination between the impellers and the front covers, the different pump sizes do not require any variation in the size or configuration of the volute.

Because a reduction of pump size from an 8 inch to a 4 inch, for example, would increase the velocity of the water flow through the passageway 44 in suction intake 12, a baffle 92 has been provided within the fluid flow passageway 44 below the opening 48 to the priming section to prevent the rapidly moving water from drawing additional water downwardly into passageway 44 from the priming system (not shown) above and adversely affecting the water flow through the pump. See FIG. 7. Baffle 92 is preferably disposed at an angle of about 25 degrees with respect to the horizontal. It has been found that by positioning the baffle below the entrance to the priming chamber, a down draft effect on the primary systems can be prevented. Such an effect could otherwise be caused by the high entrance velocity when the small 4 inch diameter hose is connected to the suction intake component. The baffle is shaped and angled in such a manner that fibrous or stringy materials are not captured by this feature.

Various changes and modifications can be made in carrying out the present invention without departing from the spirit and scope thereof. For example, the means for mounting the suction intake and front cover to the volute and the back wear plate to the volute and to the bearing housing by means of threaded studs 51 and 62 and/or the mounting of the hose attachments to the upstream flange of the suction intake could be varied so as to continue to provide readily removable and replaceable components and thereby continue to provide the pump flexibility described above and illustrated in the drawings. Other pump sizes could be provided by the present invention in lieu of or in addition to 8, 6 and 4 inch pumps. Variations in the configuration of the pump components could also be made. Insofar as all such changes and modifications are within the purview of the appended claims, they are to be considered as part of the present invention. 

What is claimed is:
 1. A variable capacity centrifugal pump assembly adapted for use with a plurality of preselected differently sized standard water inlet hoses to selectively provide pump performance characteristics associated with conventional centrifugal pumps configured for use with each of the preselected inlet hose sizes, said pump assembly comprising: a bearing housing; an impeller shaft rotatably mounted within said bearing housing and projecting therefrom in an upstream direction; a volute circumscribing a cavity therein; a plurality of differently sized impellers, a selected one of said impellers being mounted on said impeller shaft within said cavity; a wear plate secured to said bearing housing and said volute and defining a downstream end portion of said cavity; a plurality of differently configured annular front covers, a selected one of said front covers being mounted to an upstream end of said volute and defining an upstream end portion of said cavity and thereby varying the size and configuration of said cavity to accommodate a selected one of said plurality of differently sized impellers; and a suction intake mounted to an upstream end of said selected one of said front covers, said suction intake having a mounting plate at the upstream end thereof for releasably forming a sealing engagement with one of the preselected differently sized standard water inlet hoses, whereby any of said preselected inlet hoses can be sealably mounted to said upstream end of said suction intake and the capacity of the pump assembly can be varied by the selective matching of said front covers with said impellers to provide the pump performance characteristics associated with a conventional centrifugal pump configured for use with said selected inlet hose.
 2. The pump assembly of claim 1 including the plurality of spacing members, one or more of said spacing members being disposed between said volute and the selected one of said covers to maintain a predetermined spacing between the selected impeller on said impeller shaft and said volute.
 3. The pump assembly of claim 2 wherein said spacing members comprise annular discs of varying thickness.
 4. The pump assembly of claim 1 wherein said suction intake includes a body portion defining a fluid flow passageway extending axially therethrough and communicating with said cavity in said volute, said mounting plate on said suction intake being disposed at an upstream end of said body portion, a second mounting plate at a downstream end of said body portion, said second mounting plate being disposed upstream of and adjacent to the selected cover and securing said suction intake to said selected cover and said volute, a priming section mount carried by said body portion, an opening in said body portion below said mount communicating said mount with said fluid flow passageway and a baffle carried by said body portion and extending downwardly at a predetermined angle of inclination into said fluid flow passageway below said opening in said body portion.
 5. The pump assembly of claim 4 wherein said angle of inclination is about 25 degrees with respect to the horizontal.
 6. The pump assembly of claim 1 wherein each of said front covers is of an annular configuration and defines a generally cylindrical body portion, a mounting flange extending radially from said body portion for securing a selected one of said front covers to and between said suction intake and said volute, said body portions of said front covers each circumscribing a fluid flow passageway therethrough and defining an annular outwardly inclined surface proximate an upstream end of said front cover, said outwardly inclined surface merging into a curvilinear inner wall surface terminating at a downstream end of said front cover and wherein said downstream end of each of said front covers defines a fluid inlet having a transverse dimension greater than the transverse dimension defined by said inlet end of said front cover.
 7. The pump assembly of claim 6 wherein each of said covers defines a plurality of washout grooves extending through said tapered and curvilinear wall surfaces therein.
 8. The pump assembly of claim 4 including the plurality of spacing members, one or more of said spacing members being disposed between said volute and the selected one of said covers to maintain a predetermined spacing between the selected impeller on said impeller shaft and said volute.
 9. The pump assembly of claim 4 wherein each of said front covers is of an annular configuration and defines a generally cylindrical body portion, a mounting flange extending radially from said body portion for securing a selected one of said front covers to and between said suction intake and said volute, said body portions of said front covers each circumscribing a fluid flow passageway therethrough and defining an annular outwardly inclined surface proximate an upstream end of said front cover, said outwardly inclined surface merging into a curvilinear inner wall surface terminating at a downstream end of said front cover and wherein said downstream end of each of said front covers defines a fluid inlet having a transverse dimension greater than the transverse dimension defined by said inlet end of said front cover.
 10. The pump assembly of claim 9 including the plurality of spacing members, one or more of said spacing members being disposed between said volute and the selected one of said covers to maintain a predetermined spacing between the selected impeller on said impeller shaft and said volute.
 11. The pump assembly of claim 1 wherein said volute defines a water inlet end and a water outlet end and communicates said cavity therein with said inlet and outlet ends thereof and including a check valve disposed within said volute for regulating water flow therethrough to facilitate the priming of the pump and preventing back flow through said suction intake, said check valve comprising a valve cover secured to said volute, a cavity disposed in an underside of said cover, an annular valve seat removeably mounted in said volute proximate said outlet end thereof and a flexible flapper disc defining a base portion and a body portion, said base portion being disposed within said cavity in the underside of said cover between said cover and said volute and said body portion being disposed against said valve seat in sealing engagement therewith whereby water drawn by said selected one impeller through said suction intake, said selected one front cover and said inlet end of said volute abuts said flapper disc and causes said disc to flex proximate said secured base portion such that said body portion moves away from said seat to allow fluid flow therethrough and upon said valve seat becoming worn, said seat can be readily removed and replaced without the need to replace the volute. 